Complex amplitude reconstruction for dynamic beam quality M^2 factor measurement with self-referencing interferometer wavefront sensor

Abstract

A real-time complex amplitude reconstruction method for determining the dynamic beam quality M² factor based on a Mach-Zehnder self-referencing interferometer wavefront sensor is developed. By using the proposed complex amplitude reconstruction method, full characterization of the laser beam, including amplitude (intensity profile) and phase information, can be reconstructed from a single interference pattern with the Fourier fringe pattern analysis method in a one-shot measurement. With the reconstructed complex amplitude, the beam fields at any position z along its propagation direction can be obtained by first utilizing the diffraction integral theory. Then the beam quality M² factor of the dynamic beam is calculated according to the specified method of the Standard ISO11146. The feasibility of the proposed method is demonstrated with the theoretical analysis and experiment, including the static and dynamic beam process. The experimental method is simple, fast, and operates without movable parts and is allowed in order to investigate the laser beam in inaccessible conditions using existing methods.

Deep learning enabled superfast and accurate M2evaluation for fiber beams

“…Based on the results above, we can find that our scheme is accurate, robust and very fast for M 2 estimation. Compared with traditional methods [9][10][11][12][13][14][15][16][17][18][19][20][21], our approach only needs a single-shot near-field beam image collected by CCD to perform M 2 estimation, which is very economic and easy to implement under normal condition. Due to the computing efficiency of trained CNN, it only takes about 5ms to perform M 2 estimation for a single input pattern, which is a breakthrough in M 2 measuring efficiency.…”

“…In this paper, we have developed deep CNN for superfast and accurate M 2 prediction. Compared with traditional schemes [9][10][11][12][13][14][15][16][17][18][19][20][21], our approach is very economic, which only needs a CCD camera to obtain near-field beam patterns. The extraordinary time efficiency is another advantage of our scheme.…”

“…For example, the motion-free variable-focus techniques utilize spatial light modulators [10] or liquid lenses [11], leading to a measuring time below 1 s. In addition, some single-shot schemes have also been reported, with which the beam cross sections can be imaged simultaneously on detectors using a distorted diffraction grating [12] or angled Fabry-Perot filter [13] and these schemes are tested by high power Nd:YAG lasers [12] or high power fiber lasers [13] respectively. Further, complex amplitude reconstruction methods using different kinds of interferometers [14,15] or just Charge-Coupled Device (CCD) [16] are proposed. The latter scheme [16] utilizes two identical CCDs to obtain beam intensity images at different defocused positions for wavefront reconstruction, making the time taken from the image acquisition of He-Ne laser beam to the M 2 value determination only about 0.5 s.…”

Control And Numerical Simulation of Natural Convection Benchmark Type In A Cavity Heated By Laser Beam Technique Emitted From A Single Slit Diffraction

“…Sometimes, Mathematical modeling and experimental methods have been used by researchers to understand, the optical effects of laser beam penetration in the aqueous humor. These models and experiments reveal the phenomena of thermal lensing of the laser beam, various methods have been proposed for the measurement of the M2 of lasers [14][15][16][17][18][19].…”

Real-time complex amplitude reconstruction method for beam quality M^2 factor measurement

“…al. [22] also developed a new approach for real-time determination of M 2 factor by amplitude and phase reconstruction based on a Mach-Zehnder self-referencing interferometer wavefront sensor. It is simple, fast, and operates without moving parts.…”